Balloon catheters are well known for their utility in treating certain types of obstructions or occlusions in blood vessels, such as plaque build up. Angioplasty catherization typically involves aligning a balloon catheter within the vessel to position its dilatation balloon at or along the obstruction. Then, fluid under pressure is supplied to the balloon through a balloon inflation lumen in the catheter, expanding the balloon against the obstruction.
Balloon angioplasty catheters have been around since the late 1970s. Since that time the efficacy for the procedure has not significantly been improved. The restenosis rate for PTCA (angioplasty) has always averaged about 40 percent. Overinflation of the balloon can cause cracks in the intimal layer of an artery, allowing smooth muscle cell proliferation. Furthermore, overinflation of the balloon is a major cause of restenosis. In extreme cases, an aneurysm or perforation of the vessel can result from overinflation.
Overinflation of balloon catheters arises from several factors. One factor is the variety of plaque hardnesses. Atherosclerotic disease in an artery can result in plaque deposits having a wide range of hardness from "scrambled eggs" to bone. Another factor is that the profile of the obstruction is generally eccentric within the artery and does not conform to the concentric dilatation balloon profile. The physician can monitor the pressure on the inside of the balloon, but not the pressure between the outside of the balloon and the inside wall of the artery. As a result, overinflation can occur because of the concentric configuration of the balloon and the inability to assess the pressure between the outside of the balloon and the inside wall of the artery. The fluid pressure inside the inflating balloon cannot alert the physician to excessive pressure between the external surface of the balloon and the arterial wall.
The application of heat to the vessel wall during the angioplasty procedure appears to have a positive effect by requiring less force to compress the plaque against the arterial wall. Conventional balloon catheters do not provide an effective means for heating vessel walls during an angioplasty procedure. Stents are also employed in arteries. However, it is difficult to determine when the stent has been fully deployed and is in contact with the vessel wall. Current angioplasty catheters do not provide a reliable means for the physician to determine if a stent is fully deployed.
Therefore, it is an object of the present invention to provide an angioplasty balloon adapted to allow a physician to conform the balloon to an artery's inner profile, and further avoid overinflation of the balloon.
Another object of the present invention is to provide an angioplasty catheter with individually inflatable dilatation compartments that allow the balloon to assume an eccentric shape and apply different localized pressure to the different regions of surrounding artery.
A further object of the present invention is to provide an angioplasty catheter with pressure sensing capability on the balloon's external surface for monitoring pressure between the balloon and artery tissue allowing the catheter to be adaptable to treat different plaque hardnesses and to avoid overinflation.
Another object of the present invention is to provide an angioplasty balloon catheter which may be utilized for deployment of a plastically deformable stent and for controllably expanding the stent toward a custom fit to an eccentric arterial profile.
Yet another object of the present invention is to provide an angioplasty balloon catheter having thin film heaters on the outside of the dilatation balloon to allow the physician to heat the obstructed area during the angioplasty procedure, or to deploy and expand recovery metal stents by locally heating a treatment site within an artery.
A further object of the present invention is to provide an angioplasty balloon catheter with film transducers on the balloon's external surface to provide a means of intra vessel imaging.
Still another object of the present invention is to provide an angioplasty balloon catheter with perfusion lumens extending through the catheter shaft with a port located adjacent the proximal end of the balloon and another port located adjacent the distal end of the balloon, thereby allowing fluid to flow past the catheter when the balloon is expanded and in contact with the arterial inner surface.
Yet another object of the present invention is to provide dual balloon angioplasty catheter with the distal balloon opening the occlusion and the proximal balloon for deploying a stent, intra vessel ultrasonic imaging or delivering a drug to the lesion site.